Microbial infection of plants, meaning infection due to a fungal, bacterial or viral agent, is a significant agricultural problem, often resulting in pronounced loss of crop quality and useability.
Plants are susceptible to attack by a variety of phyto-pathogenic fimgi. One particularly damaging plant phytopathogenic fungus is Botrytis cinerea Pers, and plant diseases caused by Botrytis sp. are some of the most widely distributed and common diseases of greenhouse-grown crops, field crops, vegetables, ornamentals, and fruits throughout the world. One species of Botrytis, B. cinerea, is the causal agent of several severe fruit diseases, including grey mold of strawberry (Fragaria ' ananassa Duchesne) and grapevine (Vitis vinifera L.) (Agrios, 1988). Botrytis-related diseases cause losses not only in the field, but also in storage, in transit, and in the targeted wholesale and retail markets.
Other detrimental fungal plant pathogens include Fusarium oxysporum, which causes wilt in numerous plants, Sclerotinia sclerotiorum, which causes scelerotinia wilt, and Rhizoctonia solani, which can cause seedling damping off and root rot disease. Additional genera of phytopathogenic fungi include Aspergillus, Penicillium, Ustilago, and Tilletia.
The control of phytopathogenic fungi is of significant economic importance, since fungal growth on plants or parts of plants (e.g., seeds, fruits, blossoms, foliage, stems, tubers, roots, etc.) can inhibit production of foliage, fruit, or seeds, as well as reduce the quality and quantity of the harvested crop. Although most crops are treated with agricultural fingistats or-fungicides, fingal damage to agricultural crops typically results in revenue losses to the agricultural industry of millions of dollars annually.
Current control measures against plant fungal diseases include breeding cultivars for improved fungal resistance, cultural control, or the application of compounds or organisms that are toxic or otherwise antagonistic to the pathogen or towards the expression of disease symptoms.
These approaches have various problems that limit their effectiveness. For example, genetic resistance is often lacking in the desired commercial cultivars, while cultural methods, such as canopy management and reduced planting densities, are labor intensive and of limited efficacy. The application of synthetic fungicides for controlling plant fungal diseases may be expensive and have associated health risks.
The continuous economic toll taken by ph,topathogenic fungi suggests a need to develop new, more effective approaches for preventing fungal infection in plants. Additionally, these requirements should be met without significant adverse side effects to the plant or to the environment, and without seriously restricting planting or growth conditions, or requiring expensive chemical treatment of either growing plants or harvested fruit.